Аннотация
We present results from a survey for z~2.85 Lyman-Continuum (LyC) emission in
the HS1549+1933 field and place constraints on the amount of ionizing radiation
escaping from star-forming galaxies. Using a custom narrowband filter (NB3420)
tuned to wavelengths just below the Lyman limit at z>=2.82$, we probe the LyC
spectral region of 49 Lyman break galaxies (LBGs) and 70 Lya-emitters (LAEs)
spectroscopically confirmed at z>=2.82, as well as 58 z~2.85 LAE photometric
candidates. Four LBGs and 19 LAEs are detected in NB3420. Using V-band data
probing the rest-frame non-ionizing UV, we observe that many NB3420-detected
galaxies exhibit spatial offsets between their LyC and non-ionizing UV emission
and are characterized by extremely blue NB3420-V colors, corresponding to low
ratios of non-ionizing to ionizing radiation (F_UV/F_LyC) that are in tension
with current stellar population synthesis models. We measure average values of
(F_UV/F_LyC) for our spectroscopically confirmed LBG and LAE samples,
correcting for foreground galaxy contamination and HI absorption in the IGM. We
find (F_UV/F_LyC)_corr,LBG=82 +/- 45 and (F_UV/F_LyC)_corr,LAE=7.6 +/- 4.1.
These flux-density ratios correspond respectively to LyC escape fractions of
f_esc,LBG=1-2% and f_esc,LAE=5-14%, and imply a comoving LyC emissivity from
star-forming galaxies of 8.7-14.7 x 10^24 ergs/s/Hz/Mpc^3. In order to study
the differential properties of galaxies with and without LyC detections, we
analyze narrowband Lya imaging and rest-frame near-infrared imaging, finding
that while LAEs with LyC detections have lower Lya equivalent widths on
average, there is no substantial difference in the rest-frame near-infrared
colors of LBGs or LAEs with and without LyC detections. These observations are
consistent with an orientation-dependent model where LyC emission escapes
through cleared paths in a patchy ISM.
Описание
[1306.1535] Narrowband Lyman-Continuum Imaging of Galaxies at z ~ 2.85
Линки и ресурсы
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